Arctic sea ice extent hit its minimum on September 9 this year, falling to its second lowest value since satellite measurements began in 1979, according to the National Snow and Ice Data Center . More than one third (35%) of the Arctic sea ice was missing this summer, compared to the 1979 - 2000 average. This is an area about the size of the Mediterranean Sea. The 2011 sea ice minimum was very close to the all-time record low set in 2007; in fact, the University of Bremen rated the 2011 loss the greatest on record. For the fourth consecutive year, and fourth time in recorded history, ice-free navigation was possible in the Arctic along the coast of Canada (the Northwest Passage), and along the coast of Russia (the Northeast Passage.) Mariners have been attempting to sail these waters since 1497.

While the record low sea ice year of 2007 was marked by a very unusual 1-in-20 year combination of weather conditions that favored ice loss (including clearer skies, favorable wind patterns, and warm temperatures), 2011's weather patterns were much closer to average. The fact we pretty much tied the record for most sea ice loss this year despite this rather ordinary weather is a result of the fact that large amounts of thicker, multi-year ice has melted or been flushed out of the Arctic since 2007. As a result of the loss of this old, thick ice, both 2010 and now 2011 set new records for the lowest volume of sea ice in the Arctic, according the University of Washington PIOMAS model. Given the very thin ice now covering most of the Arctic, we can expect truly dramatic sea ice loss the next time 1-in-10 year or 1-in-20 year warmth and sunshine invades the Arctic. We are definitely on pace to see the Arctic virtually sea ice-free in summer by 2030, as predicted by several leading Arctic sea ice scientists. I expect we'll see more than half of the Arctic ice gone and the North Pole liquid instead of solid by the summer of 2020, and probably sooner.

When was the last time the Arctic was this ice-free?We can be sure the Northwest Passage was never open for ice-free navigation--particularly ice-free navigation for multiple years in a row--between 1900 and 2000, as we have detailed ice edge records from ships (Walsh and Chapman, 2001). It is very unlikely the Passage was open between 1497 and 1900, since this spanned a cold period in the northern latitudes known as "The Little Ice Age". Ships periodically attempted the Passage and were foiled during this period, and the native Inuit people have no historical tales of the Passage being navigable at any time in the past.

The Northwest passage may have been open multiple years in a row for ice-free navigation at some period during the Medieval Warm Period, between 1000 and 1300 AD. A better candidate was the period 6,000 - 8,500 years ago, when the Earth's orbital variations brought more sunlight to the Arctic in summer than at present. Funder and Kjaer (2007) found extensive systems of wave generated beach ridges along the North Greenland coast that suggested the Arctic Ocean was ice-free in the summer for over 1,000 years during that period. Prior to that, the next likely time was during the last inter-glacial period, 120,000 years ago. Arctic temperatures then were 2 - 3°C higher than present-day temperatures, and sea levels were 4-6 meters higher.

However, it is possible that the recent summer low-ice conditions in the Arctic are unprecedented for the past 800,000 years, according to a 2011 press release by Project CLAMER, a European group dedicated to climate change and European marine ecosystem research. They found that a tiny species of plankton called Neodenticula seminae that went extinct in the North Atlantic 800,000 years ago has become a resident of the Atlantic again, having drifted from the Pacific through the Arctic Ocean thanks to dramatically reduced polar ice. The 1999 discovery represents "the first evidence of a trans-Arctic migration in modern times" related to plankton, according to the UK-based Sir Alister Hardy Foundation for Ocean Science, whose researchers warn that "such a geographical shift could transform the biodiversity and functioning of the Arctic and North Atlantic marine ecosystems."

It is possible we'll have a better idea of historical ice-free conditions in the Arctic in the next few years. A new technique that examines organic compounds left behind in Arctic sediments by diatoms that live in sea ice give hope that a detailed record of sea ice extent extending back to the end of the Ice Age 12,000 years ago may be possible (Belt et al., 2007). The researchers are studying sediments along the Northwest Passage in hopes of being able to determine when the Passage was open during the past 12,000 years.

August 2011: Earth's 4th - 8th warmest on recordAugust 2011 was the globe's 8th warmest August on record, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). NASA's Goddard Institute for Space Studies rated August the 4th warmest on record. Land temperatures during August were the 2nd warmest on record, and ocean temperatures were the 12th warmest on record. Ocean temperatures in the Atlantic Ocean's Main Development Region (MDR) for hurricanes, from the coast of Africa to the coast of Central America between 10°N and 20°N latitude, were 0.8°C above average, the 4rd warmest August on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 6th or 3rd warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH). For more details on global extremes during August, see the details from weather historian Christopher C. Burt.

Maria hits NewfoundlandHurricane Maria hit Newfoundland, Canada yesterday afternoon near 3:30 pm local time as a Category 1 hurricane with 75 mph winds. However, the hurricane's strongest winds were over water, and the storm brought very little in the way of strong winds or heavy rain to the island. Cape Race at the southeast tip of Newfoundland saw sustained winds of 41 mph, gusting to 54 mph at 3:30 pm Friday as the center of the storm passed. Winds in the capital of St. John's peaked at 37 mph, gusting to 46 mph, at 10:30 am local time. Maria's strike makes this Newfoundland's second consecutive year with a hurricane strike, something that has never occurred since hurricane record keeping began in 1851. Last year, Hurricane Igor killed one person on Newfoundland, and damage exceeded $100 million, making Igor the most damaging tropical cyclone in Newfoundland history.

Invest 97LFor the first day since August 18, we don't have a named storm in the Atlantic. However, we have a new area to watch. A tropical wave that moved off the coast of Africa Friday and is now 300 miles south of the Cape Verde Islands is moving west at 10 - 15 mph. The wave has developed a modest amount of heavy thunderstorm activity and spin, and has been designated Invest 97L by NHC. Wind shear as diagnosed by the SHIPS model is light, 5 - 10 knots, and is predicted to stay light to moderate through Tuesday morning. Ocean temperatures are 27.5°C, one degree above the threshold typically needed for a tropical storm to spin up. Water vapor satellite images show 97L is embedded in a moist environment.

Most of the models develop 97L into a tropical depression by Tuesday; NHC gave the disturbance a 20% chance of developing into a tropical depression by Monday in their 2 pm Tropical Weather Outlook. 97L should head west or west-northwest towards the Lesser Antilles over the next six days, and could arrive in the islands as early as Friday--though most of the models predict a later arrival. It is likely 97L will encounter the usual troubles storms this year have had with wind shear and dry air on the long trek across the Atlantic.

I'll have a new post on Monday, when I'll discuss the long-range hurricane outlook for the rest of September.

Don't want to jump into a private argument, but I believe Geoff was being sarcastic. He was responding to someone else's remark. I understood it after he had explained it to someone else. That should not be directed at him, but others who had made an insentive remark. This sort of misunderstanding happens all the time on the blog, which is why i dont post much. If you read back to the earlier posts youll see what he really meant. He was defending them, not criticizing.

Quoting jpsb:Interesting, but 9" inches is pretty small (and not I am not bragging). Hard to imagine a 9" change in the tilt of a 4,000 mile ball having a noticeable effect.

Well, according to Wiki, they have a different value:

"...The principal term of nutation is due to the regression of the moon's nodal line and has the same period of 6798 days (18.6 years). It reaches plus or minus 17″ in longitude and 9″ in obliquity..."

And this: "...In addition to this steady decrease [in axial tilt] there are much smaller short term (18.6 years) variations, known as nutation, mainly due to the changing plane of the moon's orbit. This can shift the Earth's axial tilt by plus or minus 0.005 degree..."

Quoting ncstorm:I am really noticing some censorship on this blog..Two people posted private emails..one person's post was removed..the other person's email stayed where he replied at the end..when are you people going to wake up and see this blog for the hypocrisy?

Quoting BaltimoreBrian:Kublai Khan's invasion attempts were in 1274 and 1281 I believe. I'm not looking that up while doing the GFS run commentary. In Japan the typhoons that wrecked Kublai's fleets are referred to as 'kamikaze', the Divine Wind.

Yes, I know. That term was used in World War II for quite another reason.

Kublai Khan's invasion attempts were in 1274 and 1281 I believe. I'm not looking that up while doing the GFS run commentary. In Japan the typhoons that wrecked Kublai's fleets are referred to as 'kamikaze', the Divine Wind.

Quoting BaltimoreBrian:I'm thinking about doing some blogs on the influence of weather on great historic battles. Weather and Warfare. Would anyone be interested in that? Carrhae, Teutorborg Forest, Cannae, Cynocephalae. Maybe more if there is interest in it.

Was on a cruise a few years ago where a lecturer talked about the role of ocean currents in historic battles. It was fascinating. I'd enjoy anything you can come up with.

The 00Z run of the GFS at 96 hours shows 98L continuing to move west at about the same strength near 12.5 N 52 W. As a tropical depression, and it seems to have been a tropical depression for 2 days at this point.

The Cape Verde low is now moving more northwestward near 20 N 29 W at about the same strength. There is a weakness in the ridge to its north.

Quoting BaltimoreBrian:I'm thinking about doing some blogs on the influence of weather on great historic battles. Weather and Warfare. Would anyone be interested in that? Carrhae, Teutorborg Forest, Cannae, Cynocephalae. Maybe more if there is interest in it.

I'm thinking about doing some blogs on the influence of weather on great historic battles. Weather and Warfare. Would anyone be interested in that? Carrhae, Teutorborg Forest, Cannae, Cynocephalae. Maybe more if there is interest in it.

You should try to research the subject before you make a statement like that...

By COURTNEY HUTCHISON, ABC News Medical UnitSept. 1, 2011

For many of the nearly 50,000 9/11 first responders, the wounds of the Twin Tower attacks are far from healing. According to two studies published Thursday in the British journal Lancet, these rescue workers continue to struggle with respiratory illness, depression, and post traumatic stress disorder (PTSD), and many of them may be at increased risk for developing a number of cancers.

ABC News

I wanted to point out how misinformed he was. Way to set in his waysclass='blogquote'>Quoting GeoffreyWPB:

I wanted to point out how misinformed he was. Way to set in his ways.

PTSD is something you have to learn to live, with i was a firefighter for 30 years. Still pull the 12 year old boy out of the swimming pool everynight. But it was not the pool builders fault or the fence people. it just happened, so sometime when you take a job things happen to you so you need to learn to get over them

Don't want to jump into a private argument, but I believe Geoff was being sarcastic. He was responding to someone else's remark. I understood it after he had explained it to someone else. That should not be directed at him, but others who had made an insentive remark. This sort of misunderstanding happens all the time on the blog, which is why i dont post much. If you read back to the earlier posts youll see what he really meant. He was defending them, not criticizing.

At 48 hours the 00Z GFS run shows the northern low just south of Cape Race Newfoundland at about the same strength. 98L is near 12 N 42W and deeper by 1 millibar. A new Cape Verde disturbance is near 15 N 22 W.

At 24 hours the GFS shows a strong low pressure riding up the north wall of the Gulf Stream south of Nova Scotia. There is a small chance this will be subtropical. 98L is near 11.5 N 38 W as a small closed low.